The "Complex Restrictive" Pulmonary Function Pattern: Clinical and Radiologic Analysis of a Common but Previously...

Area of Science:

• Pulmonology
• Respiratory Medicine
• Clinical Physiology

Background:

• Pulmonary restriction on PFTs typically presents as simple restriction (SR) with proportional reductions in lung volumes.
• Complex restriction (CR) is an alternative pattern where FVC percent predicted is disproportionately reduced relative to TLC percent predicted.

Purpose of the Study:

• To characterize the clinical, radiologic, and physiologic features of complex restriction (CR).
• To differentiate CR from simple restriction (SR) based on PFT patterns.

Main Methods:

• Retrospective review of PFT results from patients with restriction (TLC < lower limit of normal) between November 2009 and June 2013.
• Defined SR as TLCpp-FVCpp ≤ 10% and CR based on TLCpp-FVCpp discrepancy into four classes.
• Reviewed medical records of 150 SR patients and 50 from each CR class.

Main Results:

• Of 39,277 PFTs, 4,532 (11.5%) had restriction: 6.1% SR, 4.1% CR, 1.3% mixed.
• CR patients were younger, more often women, and had higher prevalence of neuromuscular disease, extreme BMI, diaphragmatic dysfunction, bronchiectasis, CT mosaic attenuation, and pulmonary hypertension.
• CR patients had a lower prevalence of interstitial lung disease compared to SR.

Conclusions:

• Complex restriction (CR) is a common PFT pattern with distinct clinical characteristics.
• CR is associated with conditions causing impaired lung emptying, such as neuromuscular disease, occult obstruction, and chest wall limitation.
• Awareness of the CR pattern can aid clinicians in differential diagnosis.